The Columbia Center in the MLSCN will be differentiated on the basis of its strength and experience in cell biology, high content/high resolution automated cellular imaging and image analysis, and phenotypic assay design and implementation. Building on these existing strengths, our Center proposes a strategic focus on high throughput screening using phenotypic assays at the cellular and subcellular levels to identify bioactive compounds, which will enable us to meet or exceed the screening milestones mandated in the RFA within the scope of the allowed budget. Because of its strategic differentiation, the Columbia Center will perform uniquely within and to the benefit of the MLSCN network as a whole. Sister centers in the network which screen against defined molecular targets will dynamically interact with Columbia for secondary screening services. To facilitate this and to add value, the Columbia Center will draw on the assays it implements for referring investigators to create a "house repertoire" of biological assays. Profiling of hits against this repertoire of biology will provide important information on specificity at the biological level to complement information on the compound's selectivity at the protein/target level. This kind of information will be critical for the network to achieve best practice by focusing what will be limiting chemistry resources on the most promising hits. To accomplish the above goals in three years, the Columbia Center will be structured internally as a series of five functional components (assay implementation, HTS, probe development, informatics, management) each with defined goals, milestones and timelines. Each function will be led by a dedicated senior scientist, and the project will be coordinated by a dedicated project manager: The project is strongly supported by Columbia, which has already purchased a state-of-the-art highthroughput confocal cell imaging system (GE INCell3000) for the project, and will provide space (approx 5,000 nsf) adjacent to the PI's laboratory as well capital equipment needed to allow full automation of cellular screening at the Center.